1. Field of the Invention
The present invention relates to an electrically operated drive controller, an electrically operated drive control method and its program.
2. Background Art
A rotor, rotatably arranged and having a magnetic pole pair including a permanent magnet of the N-pole and the S-pole; a stator, arranged radially outward from this rotor and having stator coils of U-phase, V-phase and W-phase, etc., are arranged in a drive motor or an electric generator provided as an electrically operated machine.
An electrically operated drive unit is provided to drive the drive motor or the electric generator and to generate drive motor torque (torque of the drive motor), or electric generator torque (torque of the electric generator). A drive motor controller is provided as an electrically operated machine controller to drive the drive motor. An electric generator controller is provided as an electrically operated machine controller to operate the electric generator. Pulse width modulating signals of the U-phase, the V-phase and the W-phase generated in this electrically operated machine controller are sent to an inverter. A phase electric current generated in this inverter (i.e., the electric currents of the U-phase, the V-phase and the W-phase) is supplied to each of the stator coils. Thus, the drive motor torque is generated and the electric generator torque is generated.
For example, the drive motor controller performs feedback control using a vector control arithmetic operation on a d-q axis model in which a d-axis is set to the direction of the magnetic pole pair in the rotor, and a q-axis is set to the direction perpendicular to this d-axis. Thereby, the drive motor controller detects the electric current supplied to each stator coil, the magnetic pole position of the rotor, a direct current voltage of the inlet of the inverter, etc., and converts the detected electric current (i.e., the detection electric current) into a d-axis electric current and a q-axis electric current based on the magnetic pole position. Subsequently, the drive motor controller calculates a d-axis electric current command value and a q-axis electric current command value which are target values of the d-axis electric current and the q-axis electric current with reference to an electric current command value map. The drive motor controller further calculates a d-axis voltage command value and a q-axis voltage command value based on the deviation between the d-axis electric current and the d-axis electric current command value, the deviation between the q-axis electric current and the q-axis electric current command value, and parameters of the drive motor.
The d-axis electric current command value and the q-axis electric current command value are recorded to the electric current command value map correspondingly to drive motor target torque (a target value of the drive motor torque), the direct current voltage and an angular velocity. The parameters are calculated based on a back electromotive voltage constant MIf, a winding resistor Ra of each stator coil, inductances Ld, Lq, etc. (e.g., see JP-A-5-130710).
In the drive motor, back electromotive force is generated as the rotor is rotated. However, as the angular velocity is raised, a terminal voltage of the drive motor is also raised. When this terminal voltage exceeds a threshold value, voltage saturation is generated and the output of the drive motor is disabled.
Therefore, when the angular velocity is raised and enters a weak field control area, the electric current command value map is used to perform weak field control, and the d-axis electric current command value is increased in the negative direction in a predetermined area of high angular velocity in this electric current command value map. Thus, magnetic fluxes provided by a permanent magnet are canceled, and a linkage number of the magnetic flux to the stator coil is reduced. Accordingly, a driving area of the drive motor can be enlarged.
However, in the conventional drive motor controller, when the d-axis electric current command value becomes excessively large in the negative direction, weak field control can not be effectively performed, and drive motor torque can not be sufficiently generated.